According to the National Institute of Standards and Technology (NIST), a “hybrid cloud” is a cloud infrastructure composed of two or more clouds that inter-operate or federate through technology. In essence, a hybrid cloud is an interaction between private and public clouds where a private cloud joins a public cloud and utilizes public cloud resources in a secure and scalable way. The hybrid cloud model provides the key advantages over others cloud models, such as by allowing enterprises to protect their existing investment, and maintain control of their sensitive data and applications, as well as their network, computing, and storage resources. In addition, hybrid clouds allow enterprises to readily scale their environment on demand.
While many applications will remain within corporate datacenters, there are others whose dynamic compute requirements make them good candidates for the cloud. For such applications, the challenge is to take advantage of the computing elasticity and economics of cloud computing without sacrificing the security the information assets (e.g., database, directories, repositories) gain from being located on-premise within the business' datacenters. To be a viable hybrid cloud solution, data must be kept secure, applications need not be re-architected, and clouds should be readily mobile.